Method for producing [IrcodC1]2

ABSTRACT

A method for producing [Ir(cod)Cl] 2  is proposed, involving  
     a) Dissolving IrCl 4 .nH 2 O and/or IrCl 3 .nH 2 O and/or H 2 IrCl 6  in water;  
     b) Adding an alcohol and cycloocta-1,5-diene and  
     c) Stirring the solution at the boiling temperature,  
     characterized in that in step b) at least one alcohol is used having the formula R—OH wherein R=C n H 2n+1  and n=3-9, especially isopropanol.

[0001] The invention relates to a method for producing [Ir(cod)Cl]₂.

[0002] In the state of the art there are known several methods forproducing [Ir(cod)Cl]₂, namely by the methods of Herde (J. L. Herde, J.C. Lambert and C. V. Senoff: Inorganic Syntheses, 15 (1974), 18),Crabtree (R. H. Crabtree and G. E. Morris, J. Organomet. Chem., 135, 395(1977), Winkhaus and Singer (Güinter Winkhaus, Hellmut Singer, Chem.Ber., 99 (1966) 3610), Pannetier, Bonnaire and Fougeroux (G. Pannetier,R. Bonnaire et P. Fougeroux, Journal of the Less-Common Metals, 2191970), 437-438), and Bezman, Bird, Fraser and Osborn (S. A. Benzman, P.H. Bird, A. R. Fraser, J. A. Osborn, Inorganic Chemistry, 12, 1980,3755).

[0003] Winkhaus and Singer obtained [Ir(cod)Cl]₂ in a 45% yield byreacting Na₂IrCl₈.6H₂O or H₂IrCl₈.6H₂O with cod in a mixture of waterand ethanol after 8 to 12 hours of heating with refluxing. After theprecipitated crystals were washed with methanol the compound was driedand redissolved in dichloromethane.

[0004] Pannetier, Bonnaire and Fougeroux obtained the complex in a yieldof 85% by reacting H₂IrCl₆ with cod in a mixture of water and ethanolafter refluxing for 12 hours (no further information regarding themethod of procedure).

[0005] Bezman, Bird, Fraser and Osborn describe the synthesis of[Ir(cod)Cl]₂ by a modified method of Winkhaus and Singer. Iridiumtrichloride hydrate, hydroquinone, ethanol, water andcycloocta-1,5-diene are refluxed for 4 hours. Then the solvent ispartially distilled out and the precipitated product is filtered out,washed and dried. The yield is only 59%.

[0006] In Herde's method, iridium trichloride hydrate, ethanol, waterand cycloocta-1,5-diene is refluxed for 12 hours. After cooling to roomtemperature the precipitated product is filtered out, washed and dried.A disadvantage of this method is the low yield of only 72%.

[0007] [Ir(cod)Cl]₂ is prepared by the Crabtree method, at first withoutthe addition of water, and is then converted with aqueous sodium acetateto the desired complex compound, which is then recrystallized out ofdichloromethane/ethanol. The yield in this case is 90-95%, but itentails a multi-step procedure which is therefore complicated andexpensive.

[0008] From what as been stated, the problem arises of at leastpartially eliminating the above-stated disadvantages by means of a novelprocess. The present problem consists especially in offering a simpleand thus less expensive method for the production of [Ir(cod)Cl]₂ in ahigh yield.

[0009] This problem is solved according to the invention by a methodaccording to claim 1.

[0010] In the method of the invention, first IrCl₄.nH₂O and/orIrCl₃.nH₂O and/or H₂IrCl₆ are dissolved in water, then at least onealcohol of the formula R—OH wherein R=C_(n)H_(2n+1) and n=3-9,especially isopropanol, and cod (cycloocta-1,5-diene) are added and thesolution is stirred at the boiling temperature.

[0011] Important to the invention in the proposed method is the use ofat least one alcohol of the formula R—OH wherein R=C_(n)H_(2n+1) andn=3-9, especially isopropanol, which surprisingly in combination withwater and cod has both good solvent properties as well as givesexcellent precipitation of the end product. (The alkyl moieties of thealcohol are both straight-chain and branched moieties.)

[0012] The ordinary use of ethanol in the Herde process givesconsiderably lower yields (72%).

[0013] First, it is advantageous if the volumetric ratio of alcohol,especially isopropanol, to water is 2:1 to 1:1, since this ratio hasproven good in practice both in regard to the solubility properties ofiridium chloride, especially of IrCl₄, and also in regard to theexcellent properties of precipitation of the end product.

[0014] It is furthermore advantageous if the molecular ratio of iridiumto cod is 1:8.6, since this ratio has proven good in practice.

[0015] After the solution is stirred at ebullition the resultant[Ir(cod)Cl]₂ is filtered out, washed and dried, the solution as a rulebeing first cooled to room temperature. Such a procedure permits anexcellent separation of the [Ir(cod)Cl]₂ from the solution.

[0016] It is furthermore advantageous, since it has been proved, if thefilter cake (the desired end product) is washed with methanol,especially with cold methanol, and then dried.

[0017] Lastly, the residual solution freed from the precipitate is againconcentrated in an advantageous manner, to about 30 to 50% of itsoriginal volume and the precipitate obtained is again filtered out,washed and dried, in order thus to increase the total yield.

[0018] It is furthermore advantageous if the [Ir(cod)Cl]₂ product isground to a maximum grain size of about 0.4 mm, since this coarse powderhas good handling properties, such as a satisfactory weigh-out ability.

[0019] The following examples serve to explain the invention:

EXAMPLE 1

[0020] 10 g of iridium in the form of IrCl₄.nH₂O was dissolved indistilled water. Then 312 ml of isopropanol and 55 ml of cod were addedportion-wise and stirred at ebullition for about 19 hours. This resultedin a color change from brown toward an intense red. The reaction itselfwas performed under inert gas (in this case argon). Upon cooling to roomtemperature, shiny red crystals of [Ir(cod)Cl]₂ precipitated, which werethen filtered out and washed with a little cold methanol and dried. Theyield was 8.27 g of solid, which corresponds to about 47.4%.

[0021] The filtrate solution was concentrated to about 30%, and again abright red solid precipitated which was likewise filtered, washed anddried. Thus 7.34 g of the desired product was obtained (42.1% yield).

[0022] The total yield thus amounted to about 90%.

EXAMPLE 2

[0023] 10 g of iridium in the form of IrCl₄.nH₂O was dissolved in 150 mlof distilled water. Then 312 ml of isopropanol and 55 ml cod were addedportion-wise, and stirred for about 6 hours. A color change occurred,from brown toward an intense red. The reaction itself was performedunder inert gas (nitrogen in this case). The solution was concentratedto about 50% of its original volume. [Ir(cod)Cl]₂ crystals precipitated,which were then filtered out and washed with a little cold methanol anddried. The yield of solids was 16.23 g (about 93%).

[0024] The product obtained was rolled in a ball mill so that thecrystal size was less than 0.4 mm.

1. Method for the preparation of [Ir(cod)Cl]₂, by a) DissolvingIrCl₄.nH₂O and/or IrCl₃.nH₂O and/or H₂IrCl₆ in water, b) Adding analcohol and cycloocta-1,5-diene and c) Stirring the solution at boilingtemperature, characterized in that in step b) at least one alcohol isused of the formula R—OH, wherein R=C_(n)H_(2n+1) and n=3-9.
 2. Methodaccording to claim 1 , characterized in that in step b) isopropanol isused.
 3. Method according to either one of claims 1 to 2 , characterizedin that in step c) concentration is performed to about 30 to 50% of itsoriginal volume.
 4. Method according to anyone of claims 1 to 3 ,characterized in that the volumetric ratio of alcohol, especiallyisopropanol, to water amounts to 2:1 to 1:1.
 5. Method according to anyone of claims 1 to 4 . characterized in that the molecular ratio of Irto COD amounts to 1:7-9.
 6. Method according to any one of claims 1 to 5, characterized in that after step c) the [Ir(cod)Cl]₂ that has formedis filtered out, washed and dried.
 7. Method according to claim 6 ,characterized in that the filter cake is washed with methanol and thendried.
 8. Method according to either one of claims 6 to 7 ,characterized in that the residual solution freed of the precipitate isagain concentrated to about 30 to 50% of its original volume and theprecipitate obtained is again filtered out, washed and dried.
 9. Methodaccording to any one of claims 1 to 8 , characterized in that the[Ir(cod)Cl]₂ product is ground to a maximum crystal size of about 0.4mm.